Practice Questions: 1) A sample of magnesium is found to contain 78.70% of 24Mg atoms (mass 23.98 amu), 10.13% of 25Mg atoms (mass 24.99 amu), and 11.17% of 26Mg atoms (mass 25.98 amu). Calculate the average mass of a Mg atom. 2) Naturally occurring copper consists of Cu (mass 62.9296 amu) and Cu (mass 64.9278 amu), with an average mass of 63.546 amu. What is the percent composition of Cu in terms of these two isotopes? Discussion Questions: Pick one or more of the following and post a comment about it: 1) Pick a planet in our solar system. Research the major elements that make up that planet. What does this tell us about how and when the planet formed? OR 2) Only 17 elements have been named after people. Can you list them. Which town has had four chemical elements named after it